Viruses belonging to the human herpesvirus family induce a receptor for the Fc portion of the IgG molecule during their lytic cycle. In a continuation of our previous studies, we are presently characterizing a newly isolated receptor which binds to a staphylococcus protein A-IgG complex on HSV-infected cells. The receptor has been isolated by liquid chromatography using a protein A-IgG column and by immunoprecipitation techniques using immune and non-immune IgG. The protein is produced throughout the viral cycle is large proportions and has been identified as a HSV protein using the transblot method. This protein is located on the viral capsids as visualized by electron microscopy using protein A linked to gold. In tumor biology the phenomenon of horizontal recruitment is defined as the induction of malignancy in adjacent, presumably normal, host cells of tumor-bearing animals. We have reported a human chondroblastic tumor in a nu/nu mouse expressing a mixed composition. The bipartate tumor was injected into nu/nu rats. From the urine of the tumor-bearing rats, a transforming growth factor (TGF) of high molecular weight was isolated. The TGF is more likely of human origin because no high molecular weight TGF activity was detected in the murine cell line or in nude rats not injected with tumor. Further, all known TGF's of murine origin have a molecular weight below 20,000 Daltons and TGF with a molecular weight of 30,000-35,000 has been recently been detected in the urine of humans with disseminated cancer.